Features of PID Controller actions
Purpose of each Controller action Proportional action is the “universal” control action, capable of providing at least marginal control quality for any process. Integral action is useful for eliminating offset…
PID Tuning Recommendations based on Process Dynamics
Knowing which control actions to focus on first is a matter of characterizing the process (identifying whether it is self-regulating, integrating, runaway, noisy, has lag or dead time, or any…
Heuristic PID Tuning Procedure
From the initial open-loop (manual output step-change) test, we could see this process contains multiple lags in addition to about 2 minutes of dead time. Both of these factors tend…
Ziegler-Nichols Closed Loop Tuning Procedure
The closed-loop, or “Ultimate” tuning method of Ziegler and Nichols was applied to this process. Eliminating both integral and derivative control actions from the controller, and experimenting with different gain…
Ziegler-Nichols Open Loop Tuning Procedure
The first process tuned in simulation was a “generic” process, unspecific in its nature or application. Performing an open-loop test (two 10% output step-changes made in manual mode, both increasing)…
Recognizing an Over-Tuned PID Controller by Phase Shift
When performing heuristic tuning of a PID controller, it is important to be able to identify a condition where one or more of the “actions” (P, I, or D) is…
Recognizing a Porpoising PID Controller
An interesting case of over-tuning is when the process variable “porpoises” (Note 1 ) on its way to setpoint following a step-change in setpoint. Note 1 : The term “porpoise” comes…
Particle Image Velocimetry (PIV) Principle
Particle image velocimetry (PIV) is an optical method of flow visualization used to obtain instantaneous velocity measurements and related properties in fluids.
Ziegler-Nichols Open-Loop Method
In contrast to the first tuning technique presented by Ziegler and Nichols in their landmark 1942 paper where the process was made to oscillate using proportional-only automatic control and the…
Ziegler-Nichols Closed-Loop Method (Ultimate Gain)
Closed-loop refers to the operation of a control system with the controlling device in “automatic” mode, where the flow of the information from sensing element to transmitter to controller to…
